Mobile's browsing growth is in part a side effect of a global slump in personal computer sales as customers instead purchase smartphones and tablets, and as a result, shift their time spent online from PCs to mobile. For the year, personal computer shipments will be more than 10% lower than the year before, when shipments contracted by a then-historic 4% compared to 2011.

Usage share gains for mobile have come at the expense of what StatCounter defines as "desktop," a category that includes both desktop and notebook PCs, primary powered by Microsoft's Windows, and Macs running Apple's OS X. Desktop browser usage dropped 2 percentage points to 80% in the last three months, and fell 7 points in the last 12.

In September 2009, when Computerworld began tracking mobile browser usage -- seven months before Apple started selling its first iPad -- desktop controlled 98.9% of the usage total, according to StatCounter.

Net Applications, an Aliso Viejo, Calif.-based rival to StatCounter, also tracks desktop and mobile browsing, but uses a different methodology that essentially counts individual users, not online activity.

By Net Applications' measurement, 13.2% of all unique visitors to its clients' websites did so using a smartphone or tablet. Computerworld labels Net Applications' numbers user share to differentiate them from StatCounter's.

Personal computers accounted for 86.2% of the global browser user share for November by Net Applications' tally.

Not surprisingly, browser makers have jumped on the mobile bandwagon. Nearly 60% of Apple's November user share, as defined by Net Applications, was generated by the iOS version of Safari, for example, while 20% of Google's user share came from its stock Android browser and the newer Chrome on that mobile operating system.

Meanwhile, Microsoft's mobile version of Internet Explorer (IE) accounted for less than half of one percent of IE's total user share.

Mobile browsing reached the 20% usage share mark in November, an increase of more than 50% over the past 12 months. (Data: StatCounter.)